I suggest enlarging the photo to see the details of the copper shield properly.

The prominent ornate copper shield covers the type-bars that stand vertically behind. To print, the type-bars swing down to the top of the roller. Just before the type-bars strike the roller, they encounter a small semi-circle of metal pins for alignment purposes. Supposedly, these pins also reduce the clashing of the type-bars, but they seem to have little if any effect on either matter. Non-the-less this typewriter gets its name from these alignment pins and their function as a 'bar lock' for the type-bars.